Long-Term Investments - Additional Information (Detail) - USD ($)	3 Months Ended	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Investments Schedule [Abstract]
Auction rate securities held, at par value	$ 2,500,000	$ 2,500,000
Maturity of long-term investment		2038
Recognized cumulative losses	500,000	$ 500,000
Unrealized gains (losses) on auction rate securities		106,000	$ (43,000)
Cumulative unrealized gains	300,000	300,000
Carrying value of auction rate security	2,077,000	$ 2,077,000		$ 1,971,000
Assumed interest rate		1.39%
Estimated redemption period		5 years
Fair value input discount rate		1.50%
Recognized cumulative losses realized	$ 0